INFLUENCE OF THERMAL AND MECHANICAL TREATMENT ON THE STRUCTURE AND SUBSTRUCTURE OF TINI SHAPE-MEMORY ALLOYS

The contribution is devoted to the analysis of three TiNi-type shape memory alloys containing 49.5 at.% Ni(A), 50.4 at.% Ni(B) and 50.8 at.% Ni(C), respectively. The alloys were work hardened and subsequently annealed at 300 to 900-degrees-C/1 h/water. The transformation temperatures of different materials were evaluated by using of temperature vs. resistance dependences. The martensite B19' changes its morphology after work hardening, the occurrence of R-phase was detected in B and C alloys. Annealing of C alloys led to the precipitation of Ti11Ni14 particles and to the modification of transformation temperatures. The mobility of B2/B19' interface is limited in the case of work hardened alloys. The fundamental principles of the transformation temperatures control are determined.